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Title: Electron-beam irradiation inactivation of Salmonella: Effects on innate immunity and induction of protection against Salmonella enterica serovar Typhimurium challenge of chickens

item Kogut, Michael - Mike
item MCREYNOLDS, JACKSON - Elanco Animal Health, Inc
item He, Louis
item Genovese, Kenneth - Ken
item JESUDHASAN, P - Texas A&M University
item DAVIDSON, M - Texas A&M University
item CEPEDA, M - Texas A&M University
item PILLAI, S - Texas A&M University

Submitted to: Procedia in Vaccinology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/29/2012
Publication Date: 5/2/2012
Citation: Kogut, M.H., McReynolds, J., He, L.H., Genovese, K.J., Jesudhasan, P.R., Davidson, M.A., Cepeda, M.A., Pillai, S.D. 2012. Electron-beam irradiation inactivation of Salmonella: Effects on innate immunity and induction of protection against Salmonella enterica serovar Typhimurium challenge of chickens. Procedia in Vaccinology. 6:47-63.

Interpretive Summary: During the first week of life after hatching, the immune system of the baby chick is not very good at fighting bacterial infections such as Salmonella. Therefore, it is difficult to vaccinate baby chicks effectively against bacterial infections such as Salmonella. The objective of this experiment was to try to make the baby chick’s immune system better so that protection against bacteria can be easier. We found that giving baby chicks a killed-Salmonella bacteria will increase the ability of the chick’s immune system to respond to a Salmonella infection. In this way, the chick was able to use its own internal defenses to fight off a bacterial infection. The results of this experiment are important to the pharmaceutical industry in the United States because they show that we can vaccinate baby chicks and stimulate the chick’s immune system to protect itself from infection. In addition, there is no danger of the vaccine bacteria to grow.

Technical Abstract: Our laboratories are investigating the use of high-energy (10 MeV) Electron-Beam (E-beam) irradiation for its potential use in vaccine development. Ionizing radiation inactivates microorganisms by “direct and indirect” effects on nucleic acids and other cellular components. Though the cells are inactivated, the surface antigenic properties of the microorganisms remain unaltered. We hypothesized that E-beam-inactivated Salmonella enterica serovars could be used as a potential immune modulator to activate the innate immune response and thus reduce Salmonella intestinal colonization and shedding in neonatal chickens. Three replicate experiments were designed to evaluate the efficacy of a high-energy E-beam-irradiated Salmonella enterica serovar Typhimurium (ST) administered in ovo to induce a functional innate immune response and reduce ST colonization in the ceca of chicks three weeks post-hatch. We have previously shown that unmethylated CpG motifs of bacteria DNA oligodeoxynucleotides (CpG-ODN) given in ovo stimulates innate immune responsiveness of chicken heterophils and increases resistance of young chickens to SE colonization. Thus, they were used as positive controls in these experiments. Eighteen-day-old chicken embryos were equally divided into four independent treatment groups: (1) a negative control (sham injected, no challenge) group, (2) an infected control (sham injected, challenged) group, (3) a CpG-ODN injected, challenged positive control, and (4) an E-beam ST-injected, challenged group. All treatment groups contained 100 birds. Half of the animals from each treatment group were euthanized on day 4 post-hatch so that peripheral blood granulocytes (heterophils) could be collected to evaluate the functional innate immune response. The remaining birds where reared under normal housing conditions for the remainder of the experiment. On day 18 post-hatch, the birds were challenged with the homologous ST strain, and five days later (day 23 post-hatch), the experiment was terminated to evaluate the colonization of ST in the ceca of the birds. Differences in the leukocyte function and in the log10 cfu of ST counts among treatment groups were determined by analysis of variance. Significant differences were further separated using Duncan’s multiple range tests. Here, heterophil function was measured using in vitro assays for oxidative burst and degranulation. Heterophils from the CpG-ODN and E-beam ST-treated birds exhibited a significant increase (P < 0.05) in both the oxidative response and degranulation when compared to all other treatment groups, with no differences in heterophil functions between the CpG-ODN and E-beam-treated groups. ST colonization of the ceca was significantly reduced (P < 0.05) in both the CpG-ODN and the E-beam ST-treated birds when compared to the non-vaccinated control birds. These results demonstrate that in ovo administration of E-beam-irradiated Salmonella induced a primed heterophil-mediated innate immune response and provided a protective intestinal colonization inhibition effect against a homologous Salmonella challenge.